ISO 590 (26 x 1 3/8 E.A.3) Rims from Harris Cyclery

This is the size used on most older English 3-speeds, and imitations, including Dunelt, Raleigh, Rudge, Humber, Robin Hood, Phillips, Hercules, Triumph, Royce Union, Huffy, also fits some older 10-speeds.

This is not the rim size used by Schwinn 3-speeds, they used the 597 mm size, even though they also called them "26 x 1 3/8". This size will work with the Schwinn frames, but you will also need to replace the tires to make this upgrade.

This size is also occasionally referred to in the French sizing system, where it's called "650A". This is not to be confused with 650B or 650C, which are not interchangeable. For more on this, see my Article on Tire Sizing